In order to study the effect of nutritional stress on wool
yield, quality and efficiency of feed conversion to wool, an
experiment was conducted on Chokla and Avivastra (Exotic fine
wool type Rambouillet x Indigenous Carpet wool type Chokla)
animals. Three groups of 9 animals each of both the breeds were
offered ad libitum, 50% and 25% of ad libitum
intake of feed (50% concentrate mix + 50% ground cowpea hay),
individually for 16 weeks period. Chokla animals produced 54.9,
36.9 and 36.5% more wool with 114.2, 84.2 and 72.6% greater
efficiency in converting feed to wool in ad libitum, 50
and 25% of ad libitum intake treatments, in comparision to
Avivastra animals. Efficiency of feed conversion to wool
increased with descending level of intake in both the breeds.
Fleece weight indices at three levels of feeding remained similar
in Avivastra animals but changed significantly in Chokla animals.
Wool fibre of Avivastra animals was finer in diameter, shorter in
length and possessed more crimps/cm than the fibres of Chokla
animals. The staple length and fibre diameter reduced while
crimps/cm of fibre increased due to the effect of lower nutrition
level.

Grazing animals in arid and semi-arid regions are generally
subjected to periods of undernutrition during extreme hot
environment due to non availability of feed and poor pasture
conditions, which in turn results in low productivity. It is
important for a successful breeding programme to select the
superior animals accurately, keeping in view genetic x
environment interactions. The main components affecting
efficiency of wool production are intake, nutritive value of
feed, body weight and season (Butler and Maxwell 1984). Genetic
variation is generally maintained in wool production and
efficiency (Daly and Carter 1965; Dunlop et al 1966). The
genetic potential of higher yielding animals are exhibited fully
only when adequate feed is available (Williams 1966).

The experiment was conducted to explore the effect of ad
libitum and restricted feeding on the quality and quantity of
wool yield, and efficiency of feed conversion to wool in Chokla
and Avivastra sheep.

Materials and methods

The study was conducted on twenty-seven (27) males of 12-14
months of age, each of Chokla and Avivastra breed. The animals of
each breed after shearing were divided equally into three groups
and placed separately under a shed. Individuall feeding was
practised. Group AL was offered ad libitum feed during
10-16 h while groups AL50 and AL25 received only 50 and 25% of
their individual ad libitum intake taken during
pre-experimental period of one week. The experiment was conducted
during hot months of the year. The meteorological data are
presented in Table 1.

The animals were shorn after a period of 16 weeks and fleece
yield and body weight were recorded. Wool samples were collected
from mid side flank region of the body of the individual animals
and processed for the quality parameters.

The level of nutrition affects the wool production and
efficiency (Dunlop et al 1966; Dolling and Piper 1968; Ferguson
1972). During the 16 weeks experimental period, Chokla produced
54.9, 36.9 and 36.5% more wool than Avivastra under ad libitum,
50% and 25% of ad libitum intakes respectively (Table 2).
Weston (1965) found similar trend in high and low wool producing
groups of Merino sheep at restricted and ad libitum
feeding. The higher wool producing animals exhibit their maximum
potencial with ad libitum feeding. The results of the
experiment (Table 2) indicate that Chokla animals have better
capacity of wool production and efficiency of conversion of feed
into wool. The efficiencies of feed conversion to wool for the
period under experiment were 114.2, 84.2 and 72.6% higher in
Chokla under ad libitum, 50% and 25% of ad libitum
intake of feed. Many researchers (Moran 1970; Saville and Rabards
1972; Robards et al 1976) have found inverse relation
between efficiency and decreasing level of feeding. Efficiency of
feed conversion to wool increased with decreasing level of
feeding in both the breeds (P<0.01) and breed differences were
also significant (P<0.01). With the decline in feed intake the
increase in efficiency could be due to change in partitioning of
energy between wool and meat production as also reported by
Ferguson et al (1962).

Table 2. Effect
of feeding level on wool production in two breeds of
sheep in a hot environment (mean values and SE)

Fleece yield in relation to body weight (Fleece Weight Index -
FWI) did not change considerably in Avivastra animals. It is
indicating that change in fleece yield is proportional to the
loss of body weight at 50% and 25% levels of feeding. In Chokla
animals FWI was reduced significantly (P<0.01) at 50% and 25%
level. Thus there was considerable loss of fleece per unit body
weight during feed restriction. Although during ad lib feeding
Chokla animals exhibited full potential for wool production,
however, this breed had considerable loss of potential of wool
production than Avivastra during feed restriction; it may be due
to the fact that the animal diverts the energy for other vital
functions of the body. But it is important to note that FWI in
Chokla animals remained significantly (P<0.01) higher than
Avivastra animals at all three levels of feeding.

Table 3: Summary
of ANOVA for wool production in two breeds of sheep at
different feeding levels

------------------------
Source of Variation ------------------------

Treatment(T)

Breed(B)

(T x B)

Error

Degrees of
freedom

2

1

2

48

Mean sums
of squares

- Fleece
yield

3.3608**

2.3663**

0.262*

0.0622

- FWI

611.87**

8037.4**

345.1*

83.706

- Wool
yield/DMI

515.90**

2031.4**

13.25

25.243

- Staple
length

20.273

59.346**

3.313**

1.6951

- Crimps/cm

4.1509

12.184*

0.123

2.9411

- Fibre
diameter

111.07

232.13**

3.773

32.243

- Medullation

248.41

863.28

8.576

420.10

** Significant at 1% level *
Significant at 5% level

Wool fibres of Avivastra animals were finer in diameter,
shorter in length and possessed more crimps/cm than fibres of
Chokla animals in all the three feed regimens. The wool fibres
became fine at low level of intake in both the genotypes
(P<0.05), and the breed differences were significant
(P<0.05). This fineness of the wool under feed restriction may
be attributed tho hunger fineness. Feeding levels affected the
staple length in both the breeds; the percent reduction in staple
length was comparatively higher in Chokla than Avivastra animals.

It may be concluded that low level of feeding at 50% and 25%
of adlibitum intake reduced the fleece yield and
increased the efficiency of conversion of feed to wool.

Staple length and diameter of fibre was reduced at low level
of feeding while crimps/cm increased. Chokla animals possessed
high potential of wool production and the potential is exhibited
at higher level of feeding, while in Avivastra animals the
capacity of wool production per unit body weight did not increase
considerably with increasing level of feeding.

Daly R A and Carter H B 1955 The fleece
growth of young Lincon, Corriedale, Polwarth and fine Merino
mainden ewes under housed conditions, and unrestricted and
progressively restricted feeding on a standard diet. Australian
Journal of Agricultural Research 6:476-513

Dolling C H S and Piper L R 1968 Efficiency
of conversion of food to wool. III Wool production of ewes
selected for high clean wool weight and of random control ewes,
on restricted and unrestricted food intakes, in pens. Australian
Journal of Agricultural Research 19:1009-1028

Dunlop A A, Dolling C H S and Carpenter M T
1966 Efficiency of conversion of food to wool at two
nutritional levels by three Merino strains. Australian Journal of
Agricultural Research 17:81-89

Weston R H 1959 The efficiency of wool
production of grazing Merino sheep. Australian Journal of
Agricultural Research 10:865-885

Williams A J 1966 The efficiency of
conversion of feed to wool, during limited and unlimited feeding,
of flocks selected on clean fleece weight. Australian Journal of
Experimental Agriculture and Animal Health 6:90-95